With regards to reflow oven or furnace, when conducting a temperature profile how does one determine how many points(Parts) on the pcboard to be measured/connected to the temperature profile. And how to determine what parts to measure?

Determine the number points (parts) on a pc board to be measured/connected in temperature profile according to the purpose of the profile. For instance: * A thread here on SMTnet recently discussed �copper plate� profiling. It is used primarily for assessing the proper operation of an oven. So, maybe 5 or 6 thermocouples are used for something like that type of profiling. * When running your first piece, you may only want to use one thermocouple. * When developing the recipe for a new board, the design of the board drives much of the determination of the number of thermocouples.

In developing the recipe for a new board he goals are: * Heat the largest mass to sufficient temperature. * Keep from overheating the smallest mass component. * Be aware of heat sensitive components, such as ceramic capacitors, that should be profiled.

Where to start with the attachments? At the very least, you want to see the hottest and coldest spots on any assembly. * Hottest spot will be the PCB laminate * Coldest spot will be the largest component or a ground plane.

Points of reference are: * Review IPC-7530 - Guidelines for Temperature Profiling for Mass Soldering (Reflow and Wave) * Profiler equipment sales-types. They have briefcases full of reprints of trade journal articles written by their principals.

Guidance: * Don�t hesitate to change the location of the thermocouples, as you learn more about the board while developing your recipe. * Properly document the recipe, including thermocouple location and attachment method.

IPC [search the fine SMTnet Archives for links] sells 7530 and other documents like it.

The frequency that you check your temperature profile depends on: * Confidence that your oven is holding the profile. * Purpose of running the profile, for instance if it�s for a first piece, you check the recipe at the start of each production run and the start of each production shift change.